Process for drying smokeless powders



April 6 1926. 1,579,262

J. c. VICKERY ET AL PROCESS FOR DRYING SMOKELESS POWDERS Filed Feb. 29, 1924 A arm/a (was a? cum 77m; Fll/IP a4 own? SPRAY elm/V80? James [1 .Vi ckE H' Merle Hllavis alike-twat AT s um'rae JAMES c. vrcxnar, or nvmisvntm, INDIANA, AND man a 11. Davis, or rear PATENT orrlce.

BBAGG, NORTH CAROLINA.

PROCESS FOB. DRYING SMOKELESS POWDEBS.

' Application filed February 29,1824. Serial No. 695,935.

To all whom it may concern:

Be it known that we, JAMES (l. homer, and MERLE H. DAVIS, citizens of the United States, and residents of, respectively, Evans- 5 ville, in the cou nty of Vanderburg and State of Indiana, and Fort Bragg, in the county of Cumberland and State of North Carolina, have'invented an Improvement in Processes for Drying Smokeless Powders,

1 of which the following is a specification. 4

The subject of the present invention is a method for removing surplus moisture from materials and the invention relates specificall to a process for drying smokeless pow ers.

The primary object of the present inven tion is the establishment of a method for the production of smokeless powder of su-.

perior quality by a process more economical than heretofore used.

A further ob'ect of the invention is the establishment o a process for drying smokeless powder in which the powder can be uniformly treated so as to remove from the powder the retained solvent without injury to the ballistic qualities of the powder.

A further object is the provision of means whereby the drying process, which forms the subject of this invention, maybe carried on with the most economical employment of material. 7

With the foregoing and other objects in view, our invention resides in the novel steps comprising our process and in the details of procedure hereinafter'described and claimed, it being understood that chan' es in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

The finishingof smokeless powder which comprises its treatment from a green state to the product ready for use, consists in removing from the green powder the excess ether, alcohol, or other volatile matter which has been previously added to the powder in the process of manufacture. In the past, this removal has been accomplished by any of several different methods which have proved more or less unsatisfactory, either because of the time. required to complete the removal of the volatile solvent, or because'the powder treated will undergo frequently a change from the desired ballistic qualities.

The finishing process may be regarded as comprising .two distinct steps: first, the transference of the volatile matter or sol vent from the interior to the surface of the grain; and, second, the transference of the volatile matter or solvent from the surface of the grain to the drying medium. The first of these processes is one of diffusion and subject to the ordinary laws of diffusion, The second ofthese processes is one of evaporation and is subject to the ordinary laws of evaporation. It is obvious that the slower of the two processes is the one-which will determine the d in rate of the powder. It is the object 0 this invention to increase the slower of the two rates to the maximum value which the nature of the substance treated will permit. Since the first process is the slower and since an increase of temperature rapidly increases the rate of diffusion, we prefer to carry on our improvedprocess of drying at an elevated temperature.

While it is possible with an elevated temperature to considerably hasten the trans ference of excess volatile matter or solvent from the interior to the surface of the grain, additional precaution must be taken in order to protect the material so as to prevent alteration of the ballistic qualities of the substance treated. In particular,

it is necessary that the rate at which the solvent is transferred from the surface to the drying medium be regulated so that it will be equal to that at which the solvent is brought to the surface from the interior of the grain. In this way, it is possibleto dry at an increased rate and to obtaina finished product which will have been sub jected to uniform treatment throughout the entire section of the grain and which will therefore possess uniform, properties throughout that section.

In carrying out the process which forms the subject of this invention, the granulated powder in its green state, Will be subjected to the action of a drying medium which may consist of agaseous carrier nearly, but

not quite, saturated .with the volatile matter (ill or solvent which is to be removed from the l powder. While it has been found preferdried so that as fast as the drying medium is saturated with the volatile matter or solvent removed from the powder being dried, it willbe carried off and replaced byaddi tional unsaturated drying medium capable of taking up additional volatile natter. lVhen the powder is dried by this method, a uniform drying will be accomplished since the volatile matter or solvent present in the drying medium will prevent toorapid evaporation at the surface of the powder grains while the drying medium itself will cause a diffusion of-the solvent from the interior to the surface of the grain. In this way, powder can be dried retaining all the desired ballistic qualities.

While we prefer to carry out our process at an elevated temperature in order to produce rapid drying, it is obvious that the process may be conducted at ordinary tempera tures if the drying medium is kept below its saturation point with the solvent to be removed from thepowder.

Any suitable apparatus may be employed to carry out the process described. For the purpose of illustration reference may be had to the attached drawing, in which is shown diagrammatically one arrangement of apparatus for carrying out the process which forms the subject of this invention.

Using drying apparatus such as illustrated, the volatile matter will be conducted through the pipes 5 and 6 to a heater 7 where the temperature of the volatile matter is raised so that a suficient amount of the volatile matter or solvent to be removed from the powder may be carried'by the drying medium without saturation. From the heater, the volatile matter is conducted through a pipe 8 into a spray chamber 9 where it is mixed with a pro or amount of the drying medium. Bame p ates, eliminators, or traps 10 may be placed in the spray chamber to prevent discharge of the drying mediumv from the spray chamber with an of the volatile matter or solvent entraine therein.

From the spray chamber the drying medium shown, heating coils 13 are placed in the drier, so positioned that thedrying medium passes first through these coils before being brought into contact with the powder which has been placed in the drier on trays 14.

A circulating fan or blower 16 may be installed at any convenient point inthe system so as to insure proper circulation of the drying medium through the drier. The rapidit of circulation will depend upon the i'a-pic ity with which the drying medium ab- Hsorbs moisture from the owder. The circu- 'lation should be such t at as soon as the drying medium is saturated with the volatile matter or solvent to be removed, it passes on out of the drier so that fresh unsaturated drying medium may continue the drying action.

From the drier, the now saturated drying medium ma be conducted through a pipe 15 by means 0 a blower 16 and a pipe 18 back to the spray chamber 9 and thence into the primary conducting pipe 11.

The temperature in the spray chamber 9 is maintained at such a degree of heat that the drying medium passing therethrough is brought to a temperature sufliciently low to prevent complete saturation of the drying medium at the temperature at which it passes over the drying trays.

With apparatus such as described, continuous treatment of the powderis possible and the same drying medium may be employed over and over again so that the system described is most economical and eflicient in its action.

While it is preferred to raise the drying medium to an elevated temperature for treatment of the powder, this is not necessary since the heating coils 13 may be in corporated in the system solely for the purpose of supplying a small amount of heat and a correspondingly small degree of unsaturation in the drying medium in order that the drying medium be capable of carrying away additional solvent.

The spray chamber 9 performs two functions: It removes asmall amount of solvent from the drying medium coming from the drier and produces saturate-d gas at a slightly lower tern erature.

While a particu ar system of drying apparatus has been described, it is not intended to limit this invention to the system illustrated, since it is possible to employ other pieces of apparatus or combinations of apparatus to accomplish the purpose desired.

it should be noted that the word drying as employed in this specification has a somewhat different meaning from that ordinarily employed in smokeless powder manufacture, inasmuch as it includes the processes which been heretofore spoken of as solvent recedure which takes the een powder as delivered by the cutter an delivers it ready to be packed.

' we claim is:

While the process has been described in relation to the drying of smokeless powder,

desired to remove from a' substance contain- *ing that volatile material.

Having thus described our invention, what 1. The method of removin solvent from smokeless powder'which inc udes partially saturatinga gaseous carrier withthe solvent to be removed in a vaporized state, passing the partially saturated carrier at an elevated temperature over the powder, restoring the carrier to partial saturation and repeating the operation until the solvent in the powder has been decreased the required amount. a

2 The method of removing solvent from smokeless powder which includes drying the powder at an elevated temperature with air partially saturated with the solvent.

3. The method of removing solvent from. smokeless powder'which includes heating a desired amount of solvent, spraying the hot solvent into a gaseous carrier to partially saturate the same, raising the temperature of the gaseous carrier and passing it over the 4 powder and then restoring the carrier to a state of partial saturation and repeating the operation until the solvent in the powder has beenreduced t0 the-desired degree.

[JAMES C. VIOKERY.

MERLEv H. DAVIS.

Gil 

